Hey All,

I am having a collision problem going from a sliding collision surface to a surface that is die on contract. When the particles hit the die on contact surface most of them just break through the surface while a few die. What do I need to change to keep this from happening?

Cheers,
Nate Nesler

You could try increasing the oversampling in the collision behaviour pop.

This happens in games alot and I assume the same thing happens in Houdini. Sometimes a particle travels so fast, that it's past the collision object before a collision can be detected. Oversampling, increasing the collision sample rate, will catch more of the missed collisions, at the cost of performance though.

Are the particles still sliding on the surface when they break through? If that's the case, then you're running into the problem where particles that are flagged as sliding do not collide anymore. If not, is your killing surface moving?

Hey,

Ouch yes the particles are still sliding when they hit the surface that is suppose to kill them. That makes total since they are still flagged as sliding. Did not think of that. But how on earth do I tell them not to be sliding when they collide with the other surface. I don't have the foggest idea about how to go about that. I mean I know how to pull up their state and what not but how do you tell them to change state on a collision they don't seem to detect. I can see using an event but still you have to have something drive that event.

Cheers,
Nate Nesler

P.S. Thank You I was wondering about that good to know I am not crazying.

Hmm. That is a bit tricky. The first thing I can think of is having two particles for each of the ones in your system. The first sliding, and the second just grabbing the position and velocity from the sliding one. This second particle should then be able to collide against your killing surface and the first particle can query the “state” of the second. These duplicate particles can be deleted entirely in SOPs. Does this make sense?

Hey,

yes this makes since thats really smart. I can just assign the position of the second set of particles to be the same as the first with a position POP. That way they stay together. Or is there an easier way? Then I could add an extra Event so that when the 2nd set of particles die I can kill the 1st set based of ID numbers.

Cheers,
Nate Nesler

Yes, something along those lines. Though you're going to want to make sure you copy the velocity too as that is important when colliding.